Automatic telephone system



DW 19 1939- J. E. osTLlNE AUTOMATIC TELEPHGE SYSTEM 4 Sheets-Sheet 1 Filed Feb. l2. 1938 Dec. 19,-1939. J. E. osTLlNE AUTOMATIC TELEPHONE SYSTEM 4 sheets-sheet 2 Filed 4Feb. l2, 1938 INVENTOR. JOHN E. O5TL|NE ATTORNEYS.

DeC- 19, 1939. J; E. osTLlNE 2,183,656

AUTOMATIC TELEPHONE SYSTEM l l Filed Feb. l2, 1938 4 Sheets-Sheet 3 SELECTOR FIRST SELECTOR SWITCH BUSY TONE DIAL TONE INVENTOR.

JOHN E. OSTLINE BYM-M-MM ATTORNEY S TONE 5T.

Dec. 19, 1939.

J. E.A OSTLINE AUTOMATIC TELEPHONE SYSTEM 4 sheets-snee1`4 Filed Feb. l2, 1938 .83 uhwomu mmm lll @am ,mmm

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lem L WIS , .Qm v $55. |Ne...

INVTOR. JOHN E. OSTLlNE BY M' Qd/1.?, M

ATTORNEYS,

Patented Dec. 19, 1939 f UNITED sTATEs PATENT ortis AUTOMATIC TELEPHONE' SYSTEM Application February 12, 1938, Serial No. 190,181

32 Claims.

The present invention relates to automatic telephone systems and more particularly to improved apparatus for providing, under certain'operating conditions, operator supervision of subscribers lines terminating in an automatic telephone-exchange.

Inexisting, installed automatic telephone systems, if a subscribers line has a calling condition maintained thereon for a prolonged time interval, due to a faulty condition of the line orto the failure of a calling party to dial a desired number, only one of two results can follow. Thus, if the switching equipment in the exchange includes line lockout'apparatus, as is vsometimes the case, the calling condition created on the line will cause the line to be locked out of service until the receiver at the calling substation replaced on its hook. If, on the other hand, no such line lockout equipment is employed in the exchange, certain of the automatic switches embodied therein will be assigned to the use of the calling line and held operated until the calling condition of the line is terminated. Line lockout apparatus of the form mentioned above, when pro- 25 vided, is primarily for the purpose of preventing the automatic switches of the yexchange from being appropriated for long time intervals by lines which, due to a faulty condition thereof, have a calling condition created thereon. While perfectly satisfactory for this purpose, such apparatus does not function togive any indication to the exchange maintenance stair of the existing fault.`

In the copending application of Frederick L. Kahn, Serial No. 184,043, led Jan. r8, 1938, there is disclosed an automatic telephone system wherein provisions are made for quickly locating a line kwhich has a calling condition maintained thereon for an unreasonable time interval.

`Briefly, the telephone system therein disclosed comprises a plurality of subscribers lines, each of which is identified by a particular number or character, and a plurality of subscriber-controlled automatic switches, including at least one group of impulse responsive selector switches, for setting up connections between the lines. An emergency operators station is provided in the exchange terminating the subscribers lines, together with apparatus for establishing a connection between any calling one of the subscribers lines and the operators station in response to the continuation of a calling condition on the said one line for more than a given time interval. Specilically, this apparatus comprises a link finder 55 switch which is only operative in the levent no vcontrol impulses are transmitted .to the seized one f y of the selector switches within a given time interval after a connection has beenv established `thereto from a calling line. kEach of the subscribers lines has associated therewith line lock- .5

out means in the .form of a lockout relay, and the plurality of lines have commonly associated therewith a recording device in the form of a tape type of `pen recorder. The recording device is arranged to be controlled by any one of a 10 Agroup of auxiliary line iinder switches, individually corresponding to different groups of the subscribers lines, and an -identication switchv controlled inlaccordance with any particularv operating position assumed `by a selected auxiliary 15 line finder switch. Each ,of the line lockout relays is controllable from the emergency operators station to cause the line to be locked out of service and to initiate the operation of .the finder switch associated with-the particular group 20 of lines including the line, thereby to cause they recording device to record. the character or number identifying the lassociated line.v

While the above described arrangement is entirely satisfactory in operation, it is somewhat 2 expensive in that a considerableamount of equipment must-necessarily be provided. Specifically,

a group of auxiliary link finder switches and special trunks are required for use in routing the connections to the operators board. In addition,` 30 a `special identiiication switch is required for controlling the operation of the recording device. Moreover, the arrangement is such that a v considerable time interval kis required for the recording apparatus to record the character or 35 number of a particular line.

It is an object of the present invention to provide an improved arrangement of the general character briefly described above, which requires a minimum of special equipment and operates in a manner such that a very short-timeinterval is required for the recording apparatus completely to record the character identifying a particular line. vMore specically, it is an object of the invention to provide in an automatic exchange, improvedv and exceedingly simple apparatus for causing a connection to be established between a calling line terminating at the exchange andan operators station in the exchange both when the operators number is dialed at the calling substation and when no dialing operation Vis performed at the calling substation.

It is a further object of the invention to provide an arrangement of the character stated 55 lals wherein the same trunk line may be utilized in establishing a connection between the calling line and the operators station irrespective of whether the connection results from dialing the operators number at the calling substation or from the failure to dial a number.

The invention as described in detail hereinafter is illustrated in its embodiment in an automatic exchange which includes a dial assistance A operators switch board, hereinafter referred to as a D. S. A. operators board. This type of board is usually provided for the convenience of individuals who are unfamiliar with the method of operating the impulsing devices of the type conventionally provided at the subscriber substations of an automatic system. In the usual arrangement of this character, trunk lines, usually terminating at the bank contacts forming the zero level of the rst selector switches, are provided for routing connections to the D. S. A. operators board, so that a calling party may, by dialing the single digit zero, obtain a connection with a D. S. A. operator In accordance with one feature of the present invention, the above-noted trunk lines are also utilized for forwarding calls to the D. S. A. operators board when a calling condition is maintained on a subscribers line for more than a given time interval. The term calling condition as used herein is a generic descriptive term denoting any condition which results in the usual response of automatic switches in the exchange, whether this response be caused in the conventional manner by a subscriber lifting his receiver from its hook, by a fault in the circuit of a subscribers line, or by other means. More specically, an improved impulse generator is provided which is interconnected with each of the rst selector switches in the exchange by way of a pair of supervisory conductors and which comprises apparatus for rst applying a control pulse to one of the supervisory conductors and for thereafter impressing a predetermined series of impulses to the other conductor. The rst control pulse is utilized to condition the seized rst selector switch to respond to the series of impulses produced by the impulse generator. This series of impulses comprises the proper number of impulses to operate the wipers of the seized selector switch to a position opposite the level terminating the trunks leading to the D'. S. A. operators equipment. Thereafter, an idle one of these trunks is selected in the usual manner. A sufficient time lag is introduced between the operation of the rst selector switch and the operation of the impulse generator to enable the selector switch to perform its usual trunk selecting functions in response to impulses transmitted thereto over a calling line, provided the impulses are dialed at the calling substation within a reasonable time interval after the switch is seized. The receipt of such impulses from a calling substation serves to render the switch non-responsive to the impulse output of the impulse generator.

The control equipment for the line number recording device comprises an auxiliary primary line finder switch common to all of the lines of the system and a plurality of auxiliary secondary line nder switches, each of the latter being associated with a particular group of subscribers lines. A pulsing relay, arranged to control the recording means, is included in the primary line finder switch, which relay is connected to operate once for each step taken by the primary nder switch and also once for each step Ataken by a selected secondary nder switch. For convenience, a recording device is provided both at the D. S. A. operators board and at the wire supervisors desk also located in the exchange, these two devices being arranged to be operated in parallel so that indications are given at two different stations as to any line which is locked out of service.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawings. In the drawings, Figs. 1, 2, 3, 4 and 5 illustrate an automatic telephone system having incorporated therein apparatus constructed and arranged in accordance with the present invention.

Referring now to the drawings, the system there illustrated comprises, in general, a plurality of subscribers lines, two of which are indicated at IDI and 322, and a plurality of subscriber-controlled automatic switches, including a line finder switch IDB, a first selector switch 380, a second selector switch 3l!! and a connector switch 32B, for setting up connections between the various subscribers lines. It will be understood that a plurality of switches of each type, namely, a plurality of line finder switches, a plurality of first selector switches, a plurality of second selector switches, and a plurality of connector switches, are provided in the system for performing the usual line switching functions. The switches of each type are respectively arranged in groups, and,. in accordance with universally followed practice, the number of switches in each group is determined in accordance with the maximum volume of trafc the particular switch group is required to handle. Specifically, the exchange is designed to serve ten thousand subscribers lines, these lines being divided into one hundred-line groups with the conductors of the lines of each ii group terminating in the bank contacts of a group of finder switches and a group of connector switches. In accordance with conventional practice, each line is multipled between the corresponding bank contacts of a group of nder if,

switches and the corresponding bank contacts of a group of connector switches, whereby a plurality of such switches are available for setting up connections between each line and every other line of the system. Thus, the conductors of the line llll terminate in the bank contacts of the nder switch |03, which is one of a group of switches for serving the group of one hundred lines including the line IDI. This line, in addition to being multipled in the bank contacts of the switches in the nder switch group noted, is also multipled in the bank contacts of a group of connector switches. Similarly, the line 322. which is indicated as terminating in the bank contacts of the connector switch 320, is multipled to the corresponding contacts of other connector switches of the group including this switch and in the bank contacts of the switches in a finder switch group.

The end of each subscribers line remote from the exchange housing the switching apparatus illustrated, terminates in a subscribers substation which may be of any desired arrangement. Two such substations are diagrammatically illustrated at A and B in association with the lines mi enden, respectively. In brief, eeen of the substations may comprisethe usual hand set type of transmitter and receiver, va hook switch, a

rringer, and an impulsing device for transmittingethe switch control impulses by way of the :associated line to the' automatic switchingequipment embodied in the terminating exchange. Also associated with eachl subscribers' line-isa line'circuit, that for the line lill beingiillustrated as comprising a combined .line and two-step cutoff relay RIB!) 'and line lockoutrneans compris- As indicated above, each subscribers line has associated therewith a group of line finder switches, anyone of which is capable of establishing a link connection between the line and an associated first selector switch.

`therefore, to assign the nder switches constituting a particular groupfto successive calling ones of the lines includedv in the associated line group, there are provided allotters, that associated with the group of finder switches including the switch' HBO being indicated generally at H05.

"Since this allotter may be of any conventional arrangement, it' has been only diagrammatically illustrated in the drawings. l

Each of the line finder, rst selector, second selector and connector switches is preferably of rthe well-known Strowger type having embodied the particular arrangement of the control apparatus as embodied in the switches of different type is different' in each instance, depending upon the character of the switch. Since only the first selector switches represent a departure from conventional and well understood prior'art arrangements, the remaining switches have been diagrammatically illustrated.

Each of the first selector switches included in the system may be identical withthat vindicated generally at 300 in Fig. 3. In brief, this switch comprises a switching mechanism, indicated at 380, of the well-known Strowger type including a plurality of bank contacts arranged in levels; wipers for engaging the bank contacts; means comprising a vertical magnet 33E for stepping the wiper carriage structure vertically to position the wipers opposite a particular selected level; means comprising a rotary magnet 339 for i imparting rotary motion to the wiper carriage structure, thereby to move the wipers into engagement with a selected contact set in the selectedlevel; and means comprising a release magnet 349 for restoring the wiper carriage structure to its normal position during the release of the switch. Also incorporated in the selector switch `3M! are the usual line, hold and impulse circuit control relays RSM, R353 and Rtt, respectively, a line switching relay R330 and rotary and vertical off-normal springs indicated respectively at Sill? and M5. In addition to the conventional elements as identied above, there is provided in this selector switch a time pulse controlled relay R379 which enters into the operation'of the apparatus to perform the novel functions outlined above. For the purpose of In order,`

`signal lamp 5,3 and a vguard lamp 459. l additional apparatus provided at this station for switches to search for the calling line mi.

controlling this and the other similar relays, there is commonly associated with alll of the first selector switches a pulse generator indicated generally at 500 and described in detail hereinafter.

As pointed out in the introductory portion of the specification, provisions are-.made whereby a calling subscriber mayl obtain a connection 'to a D. S. A. operators station by dialing the single digit Zero. To this end, the tenth level of contacts in each of the first selector switches is used to terminate trunk lines extending to the D. S. A. operato-rs board. Thus, the trunk line 396l is terminated at the set of contacts 387, 388, 389 included in the tenth level of contacts, and extends to the control equipment provided at the D. S. A. operators station illustrated generally at Litt?. Each of the other trunk lines terminating at" the contact sets forming the tenth contact level of the switch 30G terminates at equipment identical to that shown in Fig. 4. trunk lines are preferably multipled to the co-rrespondingcontact sets of each of the first selector switches provided in the system, whereby a connection to the assistance operators station may be set up by way of any one of these switches.

In brief, the equipment provided at the station @mi comprises a line relay RZl), a hold relay RSll, an answer and hold key switch of the locking type, an operators cord circuit and telephone set, not shown, but connected between the These special two line conductors C412 and C473, a calling The performing the particular services outlined above comprises the recording device 478, the key switch i..

i360, and the slow-.to-release control relay R440. Neglectingfor the present the remaining apparatus illustrated in the drawings, the system as described above is, in general, entirely conventional in form and its operation is well undervstood in theart.

In brief, whenr a subscriber, such, for example, as the subscriber at they telephone A, initiates a call over the line lei to a second subscribers telephone, such, for example, as the telephone B, by lifting his receiver from its hook, a circuit isl completed for energizing the three windings of Riti) in series, this circuit extending from ground atv the supper terminal of the lower winding of Riti) by way of RAMI, CM2, the bridge across CM2 and Cm3 at the substation A, C103, RAIZZ, RCl23, RAISZ and through the upper and intermediate windings of Rlll in series, to battery. Due to the high seriesresistance of this circuit, RIS@ only partially operates to close the X contacts associated respectively with RAI33 and RAESQ. At RAESQ, ground from RAiS is applied Vto the start conductor C99, thereby to cause the allotter means m5 to initiate the operation of one of the finder At RAH33, a path is prepared for applying ground to the control conductor of the line Mil, thereby tomark the line as busy in the bank contacts of the connector switches at which this line terminates. At RAI33, battery as applied to the lower terminal of the intermediate winding of Ril is extended to the control conductor C83 terminated in the bank contacts of the finder switches, thereby to mark the line EGM as the calling lin-e. It is noted that the allotter 055 preferably functions in a manner such that an idle line finder switch is conditioned immediately to start operating in search of a calling line upon the application of ground potential to the start conductorCSS. Assuming, for example, that the finder switch is the switch assigned by the allotter |05 to the use of the calling line |0I, the wipers of this switch are first operated to a position opposite the level in which the calling line is terminated, this level being identified through the application of marking or ground potential to C99. When this level is found, the wipers are automatically stepped into the bank contact eld to test the individual lines terminating at the selected bank contact level. When the calling line, as marked by the application of battery to the control conductor C98 thereof, is found, the hunting operation is automatically discontinued and the control apparatus embodied in the switch functions automatically to switch the calling line through and establish a connection between this line and the trunk line |09 incoming to the i'irst selector switch 300. Following this operation, the line finder switch |00 is marked as busy in the allotter means |05 and the allotter means is started in operation to a position corresponding to the next available idle finder switch. Also in the course of these operations, direct ground is applied to the control conductor C98, thereby to mark the calling line as busy through the applica- Cil tion of ground to the control conductor of the line I0! and to cause the full energizaticn of the intermediate winding of R|30. As a result, Rl30 now fully operates to remove, at RA|36, ground from the start conductor C99 and to disconnect its windings from the line conductors C|02 and C103 of the line |0I. Thus, the calling line is cleared of any impedance elements which might interfere with the transmission of impulsing and voice frequency currents.

Immediately the link connection is established to the first selector switch 300, a circuit is completed for energizing the line relay R340 embodied in this switch. This circuit extends from ground on the dial tone conductor C302 by way of the off-normal springs 395 and 394, the lower winding of R340, C3I'l, RC3'I9, RA318, C3IS, RC339, RA338, Cllll, C|02, the bridge across C|02 and C|03 at the substation A, C|03, RAl22, RCl23, C|04, C|06, RA33I, RC332, C3l2, RC313, RA3'I2, C3|3 and through the upper winding of R340 to battery. Dial tone current is conducted over a path similar to that just traced and through the receiver at the substation A, thereby to indicate to the calling party that the dialing operations may be performed. At RA34| and RC343, the relay R340, upon operating, completes an obvious circuit for energizing the hold relay R350. The last-mentioned relay, in turn, operates to complete a circuit for energizing the pulse circuit control relay R360, this latter circuit extending from ground at RA353 by way of the offnormal springs 343 and through the upper winding of R360 to battery. At RA353, the relay R350 completes an obvious path for applying ground potential to the control conductor C|08 of the trunk line |09, thereby to hold the preceding finder switch |00 operated. At RA352, the relay R350 completes an obvious circuit for energizing the lower winding of the polarized line switching relay R330, thereby to render this relay exceedingly fast to operate when its upper winding is subsequently energized. At RA35I, the relay R350 prepares a test circuit, traced hereinafter, for energizing the upper winding of R330, following the operation of the switching mechanism 380 embodied in the selector switch 300 to a position corresponding to an idle trunk in a selected trunk group. At RA354 and RC356, the relay R350 prepares an impulsing circuit for energizing the vertical operating magnet 338 in accordance with the impulses comprising the first digit dialed at the calling substation A. The relay R360, upon operating, completes at RA366 and RC365 a circuit, traced hereinafter, for energizing the relay R5|0 embodied in the time pulse generator 500, thereby to initiate the operation of this generator at RA364, the relay R360 prepares a circuit, traced hereinafter, for energizing the vertical magnet 338,

The impulsing circuit for the vertical magnet 338 is completed at the beginning of the first impulse of the rst series of impulses dialed at the calling substation and when the line relay R340 restores. This circuit extends from ground at RA336 by way of RC331, RA34I, RC342, RA354, RC356, RA364, and through the winding of the magnet 338 to battery. When energized over the above-traced circuit, the vertical magnet 338 lifts the wipers of the mechanism 380 one step or to a position opposite the first level of bank contacts. Simultaneously with this operation, the off-normal springs 345 are operated to the off-normal position, whereby the above-traced operating circuit for R360 is interrupted at the springs 348, and circuits, traced hereinafter, are prepared at the springs 341 and 346, respectively, for energizing the release and rotary magnets 349 and 339, respectively. During each impulse of the first series of impulses, the vertical magnet 338 is energized in the above-described manner so that, at the conclusion of the first digit dialed, the wipers of the mechanism 380 stand in a position opposite the level of bank contacts terminating the group of trunks outgoing to the second selector switches having access to the connector switches-at which the called line 322 terminates. Each time this magnet is energized, the lower winding of R360 is energized in parallel therewith over the impulsing circuit as traced above and, due to the slow-to-release characteristic of this relay, it remains operated until the first series of impulses is terminated. For the same reason, the hold relay R350 is held operated during impulsing.

With the wipers of the mechanism 380 standing opposite the level of bank contacts terminating the group of trunks leading to the respective second selector switches of the group including the switch 3|0, the i'lrst selector switch 300 is automatically conditioned to search for an idle one of these trunks. Thus, shortly following the end of the first series of impulses, R360 restores to open, at RA364, the impulsing circuit for the vertical magnet 338 and to complete, at RA366, a circuit for energizing the rotary magnet 339. This last-mentioned circuit extends from ground at RA336 by way of RC331, RA34I, RC343, C3l5, the armature 339', C3|6, the springs 346, R036?, RA366, and through the winding of the magnet 339 to battery. Upon being energized over the above-traced circuit, the rotary magnet steps the wipers of the mechanism 360 into engagement with the first set of contacts in the selected level and simultaneously interrupts its operating circuit at the armature 339. Obviously, with this circuit open, the magnet noted restores its armature 339', to recomplete the circuit. Hence, the rotary magnet 339 operates in the manner of a buzzer to drive the wipers of the mechanism 380 over the contacts of the selected level until they are moved into engagement with a set of contacts terminating a trunk leading to an idle second selector switch. In this connection, it is noted that, if any one of the second selector 75 "iso switches is idle, this condition isindicatedbythe presence of battery potential on the control-conductor of the trunk incoming-thereto. v-In the case of a busy second selector switch, on the other hand, ground potential is present on the control conductor or" the trunk incoming thereto.A Assumingvthat the switch 3l@ is the `i'lrstl switch of the selected groupfoundfidle, the wipersl 333,335 and 333 of the mechanismf333 are rotated until they encounter the bank contacts 33 i ,1382 ands383 terminating the conductors -of 'the trunk 32! leading to this switch. Since battery potential is presenton the control conductorof this trunk, lthe upper winding of R333 is energized .over a circuit extending from ground at-RASS, by way of the upper winding noted, RAZ-55|, 03M vand the wiper 335 to battery on the contact 332, 'immediately the contacts `terminating the `conductors. of the trunk 32| are engaged by the enumerated wipers of the mechanism 383, This relay immediately operates to interrupt, at RA333, the above-traced operating circuit for the rotary magnet 339, thereby to arrest -the rotary movement of the switch wipers.

When R333 operates, it switches the partially completed connection through to the trunkline B2i extending to the vswitch 3l, throughthe operation of its armatures RA33I l-and.iRA333 into engagement with their associated contacts ARC333 andRCSsd, respectively. There isthus completeday loopcircuit `for energizing the line relay conventionally included in the-'switch/Sl, which relay, uponoperating,` causes lthe operation v01 theassociated hold relay. The last-mentioned `relay functions to apply ground to the control conductor of the trunk incoming tothe Switch 3HE which ground isextended by way Iof ythe 'contact 382 and the wiper-335 to the control v conductor C3I'f'i. -Since R333 is now. in its vfully operatedfpositiom this ground yisiiurther extended by `way oi SRA333 `to the control conductor .CIIlB` and,ihence,fserves to hold the iinder switch l in its operated position. AtRA335 the relay 113333, upon operating. completes an obvious circuit extending from' ground on C133. for energizing itsLintermediate winding, thereby to hold itself operated independentlygof the. condition vof vtlne'line and hold relays '13,3233 and R353.

At RA33l and RA338 and their respective as- -R33t, upon operating, opens vtwo points in .the `above-traced operating circuit for. R3ft,causing `this latter relay to restore. "This operation also `servesto interruptthe path for conducting dial -tone current through the receiver. at the calling substation. When R3i0ialls back, lit opens, at -RA33I and RC333, a further pointv inthe operatlingcircuit for'R35li, this latter Arelay having-been previously deenergized in response tothe opera- @esl stepped to their respective eleventh oit-normal fpositiona-v at which time the springs 390 are movedhto theuoiT-normal position. kWhenthis feccurs, an alternative circuit is completed lfor f energizing the upper Lwinding of `R36lL-thiscircuit at the. calling substation.

.pleted socia'ted Vcontacts 2RC33L2 and 'RC339, the relayextending from ,ground at RA'336 by way;of RC33'I, RA34I, RC343, the switch springs 392,

Y and through thelupper winding of R360 to battery. The relay R360, vupon operating, interrupts, at BASE@ and RCl, a point in the abovetraced operating circuit for the rotary Vmagnet :333, thereby to arrest the movement of the wipers embodied in the mechanism 333. yAt the E- normal springs 33t and 335, a point isopenedin the above-mentioned circuitforconducting dial tone current to the receiver at the calling substation, and, at the springs 393 and 39d, a circuit including thebusy tone conductor C303 is completed forconducting busy tone currentby Way of the subscribers loop circuit to the receiver The resulting lbusy tone indicatesto the calling subscriber that the desired connection cannot immediately be com- It is noted that ground as extended through thebusy tonev current transformer, not shown, to C333, is substituted for ground asapvplied to C332 through the `.iial .tone current transformer, not shown, to maintain the line relay R333 operated ollowingoperation ofthe springs 333 to theolT-normal position.

The calling subscriber, upon receiving busy tone, ,may initiate the release of the operated .switch train by restoring his receiver to itsghook to open `the loop circuit over which the linejrelay R333 is heldoperated.r This relay, upon restoring, opens, atRA33I and RC3I3, points-in, the above-traced operating circuits for .theJelays R353 and R333. These two relays, restore, after an interval, to complete a circuit for energizing the release magnet 349, this circuit Aextending from ground at rRll33i by wayof R033?, RA34I,

`395332, RA3543, RC355, RAS, RC33, the Switch springs 313i, Vand through the winding of the magnet. 339 to battery. In response to the enervgizationof the release magnet, the wipers ofthe mechanism 33B are restored to normal, at which time the oil-normal .springs 345 and r336 are returned to normal. When the hold relay .R353 restores, ground isremoved. atr RA353 from the control conductor C I 630i the trunkI 3S incoming to the selector switch .333, thereby to release the line finder switch it!) and cause the restoration of the combined .cutoi .and line relay RI30.

Thus, the partially completed connection "is cleared out and the switches involved therein are released for further use.

Continuing now with the. operation of the apparatus toy establish. a connection tothe called `line 322 and assuming that the second selector it will be understood that the second dialeddi'git .results'in the elevation of the wipers of the switch 3m to a position opposite the level of bank contacts terminating the trunksleading to thelconnector switches having access to thecalled'line. Following this operation, the wipersof the vswitch 3H] are automaticallystepped over. the contacts of theselected level until a trunkv leading tojan idle connector switch of the selected 'group is found.` Assuming, for example, lthatthe connector switch 323 is the rst idle connector switch in the selected group, when the .wipersfof the connector switch, the subscribers loop circuit is extended thereto to cause the operation of the line and hold relays conventionally provided therein, whereby ground is returned over the control conductor of the selected trunk to hold operated the switches 3I0, 300, and I00. With the apparatus in this condition, the connector switch 320 is conditioned to respond to the impulses comprising the third digit dialed at the substation A. In response to the dialing of this digit, the Wipers of the connector switch 320 are stepped vertically opposite the level of bank contacts at which are terminated the lines of the ten line group including the called line 322. Following this series of impulses the connector switch is conditioned to rotate the wipers step by step in accordance with the impulses making up the fourth and final digit dialed at the calling substation. When the last digit is dialed, the wipers of the switch 320 are stepped into engagement with the set of bank contacts terminating the called line 322. In accordance with conventional practice, suitable provisions are made for testing this called line to determine its idle or busy condition; for returning busy tone over the established loop to the calling subscriber in case the line is busy; vand for applying ringing current to the called line in the event this line is idle at the time it is selected. Assuming that the called line is idle, the desired conversational connection is established when the called substation B is answered.

Any desired arrangement of the connector switches may be used for insuring the release of the switch train following the completion of a talking connection by way thereof between two subscribers lines. Thus, the control apparatus embodied in this switch 320 may be arranged so that the release of the connection is under the control of the calling party or, alternatively, undervthe control of the last party to hang up. In either case the release of the switch train is initiated upon the restoration of the hold relay conventionally provided in the connector switch 320, this operation serving to remove holding ground from the control conductors of. the various operated switches, thereby to cause the energization of the release magnets respectively provided therein in a manner similar to that described above with reference to the release of the lirst selector switch 300. During the release of the switch train and when ground is removed from C98, the holding circuit for RI30 is opened causing this relay to restore. When this occurs, ground is removed from the control conductor of the line IOI, thus identifying this line as idle in the bank contacts of the connector switches at which the line terminates.

As pointed out in the introductory portion of the specification, provisions are made for routing a connection from a calling susbcribers substation to a D. S. A. operators station upon the dialing of a predetermined digit at the calling substation. If, for example, a party at the substation A desires the assistance of. an operator in completing a connection to another subscribers line, such assistance may be obtained by initiating a call in the usual manner and dialing the single digit zero. If it be assumed that the finder switch and the associated iirst selector switch 300 are assigned by the allotter I05 to the use of the calling line, the apparatus in the switch 300 is conditioned to respond to the impulses of the dialed digit, following the operation of the finder switch to iind the calling line and to switch the connection through to the trunk line |09 in the manner set forth above. Thereafter, and when the predetermined digit zero, comprising ten impulses, is dialed at the substation A, the wipers of the mechanism 380 are translated vertically to a position opposite the tenth bank contact level wherein the trunks extending to the D. S. A. operators board are terminated. Following this operation, the wipers are automatically rotated successively to test the trunks of this group for the purpose of selecting a trunk leading to an operators station which is not in use. From a consideration of the apparatus illustrated in Fig. 4, it will be seen that, if the apparatus at any particular station is in use, the control conductor of the trunk line leading to this station has impressed thereon ground potential, whereas, if the apparatus is idle, battery potential is impressed on the control conductor of the trunk incoming thereto. Thus, with the apparatus at the station 400 idle, the line relay R420 and the hold relay R430 are restored, so that battery potential is extended through the resistor 462, RC 434 and RA432 to the control conductor C398 of the trunk 398. When, on the other hand, the apparatus at this station is busy, the two relays noted are energized and ground at RA43I is extended by way of RC44'I, RA446, RC433 and RA432 to the control conductor C398.

The operation of the selector switch 300 to test the several trunk lines terminating at the zero level of bank contacts is exactly the same as that described above with reference to the operation of the apparatus during a call from the substation A to the substation B, and, hence, need not be repeated. Assuming that the trunk line 396 is the rst idle trunk line of the group terminating at the zero level of bank contacts, when the wipers of the mechanism 380 encounter the contacts 381, 388 and 389, the hunting operation of the selector switch is interrupted through the operation of R330, which relay also functions to extend the subscribers loop by way of the line conductors C391 and C399 of the trunk line 398 to the operators station, thereby to complete a circuit for energizing the line relay R420. This relay, upon operating, completes, at RA42I, an obvious circuit for energizing the slow-to-release hold relay R430. The hold relay, in turn, completes a path extending by way of RA43I, RC44'I, RA44S, RC433, RA432 and C398 for applying ground to the control conductors of the operated switches 300 and |00, thereby to maintain these switches operated. The presence of ground on C398 marks the trunk line 396 as busy in all of the other first selector switches at which this line is terminated, thereby to prevent the apparatus at the station 400 from being seized on another call to the D. S. A. operators board initiated before the release of the apparatus provided at the station 400. At RA43 I, the relay R430, upon operating, completes a circuit for energizing the call lamp 458, this circuit extending from ground at RA43I by way of RA442, RC443, the switch springs 456 and 455, the switch springs 453 and through the filament of the lamp 458 to battery. The resulting illumination of the lamp 458 gives a visual indication to the operator at the station 400 that an incoming call awaits attention. To answer the call, the operator actuates the key switch 450 to its answer position, thereby to complete a talking connection to the calling substation. More specifically, when the key 450 is operated to its right olf-normal position, the springs 45I 2,183,656 and' 45'2 are moved intov engagement, effectively v to connect the conductors C412 and C413, ex-

tending to' the operat'ors telephone, to jthe line cohdu'ctorsCSSl and C399, respectively, of the trunk line 396. At the springs 453, the aboveltraced circuit for energizing the signal 'lamp 458 is opened.

Following receipt of the information as to the line desiredby the calling subscriber, the operator may either advise the subscriber as to the method' of dialing'thejdesired number, or set up'the desired-connection inthe manner conventionally lemployed in exchanges of the man- If the operator desiresy to hold the' f ual type. connection to the calling line while calling 'another line, she may operate the key switch 450 to the -hold position, thereby to prevent the switch train from being released even though the calling party hangs up. When this vkey is operated toits left' oli-normal or hold position, anH obvious h'olding'c'ircuit extendingfrom ground at .the springs 454 is completed for maintaining the hold relay R430 operated independently of the line relay R420.

Thus, the connection can not be clearedout even though the calling, subscriber hangs up. When the key 450 is operated to its hold position,` thesprings 455 and 45G'are opened to interrupt the above-traced circuit for the lamp 458 and the springs 453 and 451 are closedV to complete a circuit for energizing the guard lamp 459. The last-mentioned circuit extendsv from ground at RA43| by way of RA442, RC4'43',.the springs 456` and 451 and through i the filament of the lamp 45t to battery. Obvi- S'ously, if the key 458' is thereafter operated to I the answer position, lthe vabove-traced holding circuit for R430 is opened, the energizing cir- `cuitfor the lamp`459 isA opened, and the yoperating circuit for the lamp 458 is opened. If the calling subscriber has previously restored his receiver to its hook,- the operationfof the key 450 from the hold position to theanswer position results in the" release of the established connection,` sinceunder this condition the line relay R420 isdeenergized and no circuit isavailable for holding R430 operated.v

The release of a connection established rto the operators station 4001s entirely under the control of thel calling subscriber providing the key 45'is'not operated toits hold position. Specically, when the" calling subscriber restores his recei'Ver'to its hook, the 'loop circuit over which R1420isv held operated is opened, causing this relayto restore. When R429 restores, it opens the operating circuit' for R430 and the latter. `relay, upon restoring, removes holding ground from the control conductor C398. Thus, thev operated switches 30u and |00, and the combined lineand cut-off relay BIBB are caused to restore 6.09111 the manner pointed out above. Y'

and the trunk lines interconnecting this board with the various first selector switches, an im- .pulse generator `50i) for causing any one of the l the D.A S. A. operators boardl in' the event a call-n ing condition is maintained on the calling line vtr irst selector switches tojroute the connection to for an unreasonably long predetermined time interval; 'Ihi's apparatus also includes a recordingv` device llllvloca'tedv atl the yD; SpA. operators"board,l

a similar recording device 260, which is located at a second telephone station, preferably the wire chiefs desk, and a plurality of auxiliary nder switches for causing each of the two recording m devices Mitiy and 470 to register the number or 5' character identifying a calling subscribers line in response to the partial operation of theline' lockout relay R121) associated with the line Elli, or a corresponding relay associated wtih any one of the othersubscribers lines. More particularly, there isprovided aprimary nder switch 200, which is commonly associated with all of the pluralityof subscribersV lines terminating in the\ exchange, and a plurality of auxiliary secondary line finder switches, one of which is indicated vat i90, which are respectively associated with different groupsof two hundred subscribers lines.

LFach of' the auxiliary line lnder switches is of ,the well-known Strowger type, similar in all respects to the finder switch diagrammatically illustrated at IGS. Thus, the primary auxiliary iinder switch Edil comprises a switching mechanism 2l@ which includes a plurality of bank contacts arranged inlevels, and a set of wipers 21,

- Zilli", 286 and 283 adapted to be translated vertically opposite ra selected contact level by means comprising a vertical operating magnetl 295 and thereafter to berotated into engagement witha selected set of contacts in the selected level by means comprising a rotary operating magnet 2%. 3 'i thev purpose of selecting a desired level of contacts, there is `also included in the switching mechanism a set of test contacts 284, individual ones of which are oppositely disposed' with reyspectto the various Contact levels, and a test/3K erally at 2%.y Therelay R25@ is a pulsing relay which is connected and arranged to operate once during each step taken by wipers of the switch' 26sl during the vertical andl rotary movements thereofA and also once during. each step taken by the Wipersv embodied in any selected one of the 56? auxiliary secondary nder switches. It is through the operation of thisrelay that the two recording devices and 4l@ are caused to record the number or character identifying a particular calling line.

Each-ofthe auxiliary secondary finder yswitches is s'ulostantia'llyv identical with the primary finder switch 2M) insofar'as its construction and arrangement is concerned. Thus, the switch 96 comprises a'switching mechanism i55, which in- 6U' cludesa plurality of bank contacts arranged in levels andV a set of wipers l5?, 85?', E59 and IEE?" which are adapted to be translated vertically opposite a particular contact level through theoperation of a vertical rmagnetl H8 and vthereafter 6"'5"vk to be rotated into engagement with a selected set of contacts in the selected level by means comprising a rotary magnet lll. A set of test con-v tacts l i3, the'in'dividualA ones'oi which are oppositely disposed with respect to the'various contact 705 levels, and a test wiper yl i4, arranged successively to engager the contacts ofthe set llt as the wiper carriage'structure is translated vertically through theoperation ofthe magnet 118; are provided for thepurposepf selecting afdesired marked 'level 'fili4 yrotary switch 590, the relay network noted and zoA of the bank contacts. For the purpose of releasing the wiper carriage mechanism following its operation to a particular position, there is provided a release magnet 116. This switch further comprises a set of off-normal springs indicated generally at 180 and four control relays RI40, R150, R160 and R110, the first three of which comprise means for causing the full operation of any lockout relay associated with a calling line included in the group of lines corresponding to the switch 100.

The recording devices may be of identical construction and of any desired form which responds to pulses of ground potential applied to one of its input terminals. One type of recording device well suited to the present application is the wellknown pen recorder which conventionally comprises a stylographic pen arranged to have its marking tip moved into engagement with a recording tape moving at uniform speed, thereby to make a mark or dash on the tape, each time the operating magnet embodied in the recorder responds to a ground pulse applied to one of the input terminals of the recorder.

As pointed out above, the primary nder switch 200 is commonly associated with al1 of the subscribers lines terminating at the exchange. This switch responds to the partial operation of any one of the lockoutl relays associ- :ated with the respective subscribers lines and functions, during the vertical movement of its wipers, to select the particular group of one thousand lines which includes the calling line and, during the rotary movement of its wipers, to select the particular group of one hundred lines which includes the calling line. Through this last-mentioned selection, the primary nder switch incidentally selects the auxiliary secondary nder switch associated with the group of lines including the calling line. Each of the latter switches is capable of selecting any one of a group of two hundred lines, but, when conditioned for operation following the operation of the switch 200, is confined in its operation to a determination of the particular subgroup of ten lines in the previously selected group of one hundred lines which includes the calling line, and to a determination of the calling line in the selected subgroup of lines. The particular mode of operation of the switches to select a particular calling line is pointed out more in detail hereinafter.

Considering now the arrangement of the apparatus making up the novel impulse generator 500, it is pointed out that this generator comprises, in general, a start relay R515 under the control of a time delay device indicated as a dashpot relay R510, a pair of output terminals 591 and 508 and a relay network comprising the relays R520, R530, R540 and R550, which operate in response to the operation of the start relay to impress a control pulse on the output terminal 591 a predetermined time interval after the dashpot relay R510 is energized. This generator further includes apparatus comprising a four relays R550, R560, R510 and R580 for impressing a predetermined number of impulses on the other output terminal 598 following the application of the control pulse to the terminal 591. Each of the two relays R540 and R510 is of the well-known pendulum type and includes a weighted armature which, when attracted and thereafter released, vibrates, pendulum fashion, periodically to make contact with its associated contacts.V` The switch 590 is of the well-known rotary type and comprises two sets of bank contacts 591 and 592 of eleven points each, wipers 593 and 504 respectively associated with the enumerated contact sets, and means comprising an operating magnet 595 and a ratchet and pawl mechanism, not shown, for driving the wipers over their respective associated contacts.

Operation of the impulse generator 500 Before describing the operation of the apparatus to extend a connection to the D. S. A. operators board when a calling condition is created on one of the subscribers lines and no impulses are transmitted thereover, the operation of the impulse generator 500 will be considered. This generator is started in operation immediately any one of the first selector switches is seized, and continues to operate until the'wipers of the seized selector switch are translated vertically to a position opposite the selected level and the trunk hunting operation is started. Thus, when R300 operates in the sequence of operations described above, it completes a cir-v gizing the start relay R515. The circuit noted extends from ground at the upper terminal of the winding of R515 by way of this winding, RA518, RC51'9 and through the springs 512 to battery. The relay R515, upon operating, completes a holding circuit for itself in series with the rotary magnet 339, this circuit being similar Lto that traced above for R515 but differing therefrom in that it extends by way of RA511, RA518 and the winding of R515 to ground rather than by way of RA516 and the winding of R510 to ground. Due to the high resistance of the winding of R515, the rotary magnet 330 does not operate when energized in series with this Winding. At RA516, the relay R515 opens a point in the operating circuit for R510 and, at RA518 and RC519, it opens a point in its own operating circuit.

At'RA510, the relay R515 completes an obvious circuit for energizing the pendulum type relay R540, causing the latter relay to attract its weighted armature RA541 to complete a circuit for energizing the slow-to-operate relay R530. The last-mentioned circuit extends from ground at RA541 by way of RC543, RC542, and the winding of R530 to battery. The relay R530 operates, after an interval, to prepare, at RA531, a holding circuit for itself, and to complete, at RA532, a circuit for energizing the slow-to-operate relay R520, this latter circuit extending from ground on the wiper 593 by way of the rst contact of the contact set 501, RA532, RC533 and through the winding of the relay R520 to battery. The relay R520 now operates to prepare, at RA522, a, circuit'for energizing R550 and to open, at RA521, a point in the operating circuit for R540. With R540 deenergized, its armature RA54l is released and starts vibrating, pendulum fashion, alternately to make contact with RC544 and to insure its engagement with the two contacts RC543 and RC54ll.y When the amplitude of vibration of RA54I is reduced to a point where this armature no longer engages the two contacts noted, the holding circuit for R530 is opened and this relay restores to complete a circuit for energizing R560. The last-mentioned circuit eX- tends from ground at the switch wiper 593 by way of RA532, RC534, RA522, RA552, RC553 and through the winding of R560 to battery. The relay R530, upon restoring, also opens, at RA532 and RC533, the operating circuit for R520, causing this relay to slowly restore to recomplete, at RA52I, the operating circuit, traced above, for R540 and to open, at RA522, the operating circuit for R560. Before R520 restores, however, R550 operates to complete a circuit for holding itself energized in series with the upper winding of R550, this circuit extending from ground at RA5I9 by way of the switch wiper 594, the first contact of the contact set 592, the upper winding of R559, RA50! and through the winding of R560 to battery. The relay R590, upon operating, also applies a'control pulse to the output terminal 591 to which is connected the supervisory condiuctor C304. Specically, this pulse consists in the application of ground potential to the terminal 591 over a path extending by way of RA551 and RA563. Shortly thereafter and when the winding of R560 is connected in series with the upper winding of R550, the last-mentioned relay operates to open, at RA55I, the path for applying ground to the terminal 591. This operation serves to conclude the control pulse applied to the terminal noted.

When the relay R560 operates, it completes, at RA562, a circuit extending from ground at the switch wiper 593 for energizing R510, causing the latter relay to attract its weighted armature RA51I to open points in the respective circuits, traced hereinafter, for energizing the relay R590 and the operating magnet 595 of the switch 599. At RA552, the relay R550, upon operating, opens a point in the operating circuit for R560 and prepares a circuit for energizing the operating magnet 595 of the switch 590. At RA555, the relay R550 prepares a point in the common portion of circuits, traced hereinafter, for energizing the pulsing relay R580, the pendulum type relay R510, and the magnet 595.

When the relay R520 restores to recomplete, at RA5ZE, the operating circuit for R540, the second cycle of operation of the three relays R520, R530 and R500 is started. The relay R540, upon v operating, completes the above-traced circuit for energizing R530, which latter relay, in turn, reoperates to complete the operating circuit for R520. Due to the vibration of the weighted armature RA54I, the two relays R530 and R529 are held energized for a predetermined time interval, at the expiration of which R530 restores to open the operating circuit for R520.

When R590 restores during this second cycle of operation of the three relays noted, a circuit is completed for energizing the operating magnet 595, this circuit extending from ground on the switch wiper 593 by way of RA532, RC534, RA522, RA552, RC559 and through the winding of the magnet 595 to battery. When energized over the above-traced circuit, the magnet 595 attracts its armature, thereby to condition the associated ratchet and pawl mechanism to step the wipers 593 and 594 to their respective rst off-normal positions. Shortly thereafter and when R520 restores, the above-traced energizing circuit for the magnet 595 is opened, causing the two switch wipers noted to be stepped into engagement with their respective associated second contacts. When this occurs, the above-traced circuit over which R550 and R550 are held energized is opened at the switch wiper 594, causing R560 to restore. The relay R550, however, is held operated since a new circuit is completed for energizing its lower winding simultaneously with the interruption of the energizing circuit for its upper winding. The circuit noted, namely, that for energizing the lower winding of R550, extends from ground at RA5| 9 by way of the switch wiper 594, the second contact oi the set 592 and the lower winding of R550 to battery. `At the switch wiper 593, the above-traced operating circuit for the pendulum relay R510 is interrupted, causing this relay to release its weighted armature RA51. This armature now starts to vibrate to deliver ground pulses to the magnet 595 and the pulsing relay R580. Specifically, each time RA51I engages its two associated contacts RC512 and RC515, circuits extending from ground at RA555 are completed for energizing R580 andthe operating magnet 595. Each time RA51I engages its associated Contact RA512, a priming circuit is completed for energizing R510, this circuit extending from ground at RA555 by way of RA51I, RC512, the resistor 59B and through the winding of R510 to battery. By virtue of this arrangement, the weighted armature RA51G is caused to vibrate continuously at a iixed rate, this rate being of the order of ten vibrations per second. Each time a ground pulse is delivered to the operating magnet 595, this magnet steps its wipers one step and, each time a ground pulse is delivered to the pulsing relay R580, this relay 0perates to disconnect, at RA584, ground from the output terminal 590 terminating the supervisory conductor C308. When the wipers of the switch 599 are returned to their respective home positions by the operating magnet 595 and its associated ratchet and pawl mechanism, the abovetraced holding circuit including the lower winding of R559 is interrupted at the switch wiper 599, causing this relay to restore. When R550 restores its armature RA555, operation of the switch 599 and of the impulsing relay R580 is arrested, since ground for completing the respective operating circuits for these elements is no longer present on RA51i. The restoration Aof R550 further results in the deenergization of R510 so that RA51E gradually assumes its resting position wherein it engages its associated contacts RC512 and RC513.

During the interval when the pendulum relay R570 is operating to deliver pulses to the magnet 595 and the impulsing relay R589, the cyclic operation of the three relays R520, R590 and R540 is interrupted. Thus, immediately the switch wiper 599 is stepped from its home position, a point is opened in the operating circuit for R520 so that this relay can not operate following the sequential operation of the two relays R540 and R530. Hence, no further operation of the three f relays noted occurs until such time as the wipers ofthe switch 590 are returned to their respective home positions. If the start relay R5l5 is still operated when the switch wipers 593 and 594 are returned to their respective home positions, the above-described sequence of operations is repeated. Thus, immediately the switch wiper 593 engages the first contact of the contact set 59| and with the two. relays R530 and R500 operated, the above-traced circuit is completed for energizing R520. From this point on, the operation of the apparatus is identical with that described above.

Once the switch 590 starts to operate, the wipers thereof are driven through a complete cycle independently of the position of the start relay R515, but immediately this start relay restores the operation oi the pulsing relay R580 is arrested. Thus, if the start relay restores after ve ground pulses have been delivered to R580 and the operating magnet 505, the holding circuit for the relay R550 is opened at RA5l9, causing R550 to restore to open, at RA555, a point in the common portion of the circuits for delivering pulses to the magnet 595 and the pulsing relay R580 thereby to prevent further operation of the pulsing relay. When R550 restores, however, it completes a circuit for energizing the magnet 595 by Way of the self-interrupting contacts associated with the armature 596, this circuit extending from ground on the wiper 593 by way of any one of the multipled contacts of the contact set 59l, the armature 596, RC558, RA556 and through the winding of the magnet 595 to battery. Due to the circuit interrupting action of the armature 505, the magnet 505 is repeatedly energized to drive its wipers to the home position, at which time its operating circuit is opened at the switch wiper 503. Obviously, if the start relay R5l5 is deenergized following the application of the control pulse to the output terminal 591 and before any impulses are impressed on the terminal 598, further operation of the impulse generator is prevented. This is true for the reason that ground from RA5I9 is relied upon to maintain the relays R520, R530 and R540 operating and to hold operated the two relays R550 and R560.

Operation of the apparatus to extend a connection from a calling Zine to the operatorie station when no impulses are transmitted over the calling line f Referring now more particularly to the operation of the apparatus automatically to extend a connection to the D. S. A. operators board when a calling condition is created on one of the lines and no impulses are thereafter transmitted thereover, the iirst selector switch 300 in its operation to extend a connection from the calling line l0! to the called line 322 will again be briefly considered.

Immediately the link connection is established to this selector switch from the calling line, the relay R300 operates to initiate the operation of the impulse generator 500 in the manner described above. When R350 operates, it also prepares, at RA350, a circuit, traced hereinafter, for energizing R310 in response to the application of a control pulse to the output terminal 501 of the impulse generator 500. If the calling condition on the line i i is occasioned by a fault on this line or by an emergency at the substation A, such that the callingr subscriber is unable to operate the dialing device located at this station, no impulses will be transmitted by way of the calling line and the established link connection to the seized first selector switch S00. Hence, only the relays R340, R350 and R350 of this switch are operated. After this condition has prevailed for a given time interval, the relay R560 embodied in the impulse generator 500 operates in the manner described above to apply a ground pulse to the supervisory conductor 0305i. This pulse serves to energize R310 over a circuit which extends from ground on the conductor C304 by way of the switch springs 30|, RAiiS, RC315, RA314 and through the winding of R310 to battery. The relay R310, upon operating, completes a holding circuit for itself, which circuit includes the conductors of the loop extending to the calling subscribers substation. Speciiically, this circuit extends from ground at RA311 by way oi RAB'l, C3l8, ROSSE", RASEE, CI01, Cl02, the bridge across CEDE and Cm3 at the calling substation, C503, RA522, RClEB, Cl04, CH3", RA33l, RC3-32, C2H2, RA315, RA314 and through the winding of R310 to battery.

With R3i0 operated, the previously traced operating circuit for the line relay RSM! is interrupted at RAE??? and RA310. The relay R340 is, however, held operated over an alternative circuit which extends from ground at RA5Sll by Way of C335, RAS'H, RA312, C3l3 and through the upper winding of R305 to battery. This circuit constitutes an impulsing circuit by way of which the line relay Rllii is made to respond to the impulse output of the impulse generator 500. Thus, each l time R500 operates, it opens, at RA534, a point in the impulsing circuit, just traced, to cause R345 to restore. Since with R355 and R360 operated, an impulsing circuit is prepared to the vertical magnet 330, thismagnet is energized in accordance with the pulses produced by the generator 500 and translates the wipers of the mechanism 380 to a position opposite the bank contact level correspending to the number of impulses produced by tenth bank contact level, or the level terminating the trunk lines extending to the D. S. A. operators board. Thereafter and when R350 restores, the trunk hunting operation oi the selector switch is initiated to select an idle one of these trunk lines. Assuming that the trunk line 300 is the` first idle line available, when the wipers 384, 385 and 335 are driven into engagement with the contacts 381, 383 and 389 terminating the respective conductors of this trunkl line, the relay R330 is caused to operate to interrupt the trunk hunting operation of the selector switch 300 and to switch the subscribers loop through to the operators station @00. In response to this operation, R420 and R430 operate, in the order named, and the last-mentioned relay returns ground over the control conductor C300 te hold the selector switch the nder switch 00 and the relay R! 30 operated. When the hold relay R430 operates, it completes, at R, 113i, the previously traced circuit for energizing the call lamp d50. The apparatus remains in this condition until the call is answered at the operators station.

It is pointed out that, if the calling condition on the line l0! is removed before the generator 500 starts to deliver pulses to the line relay R340, the selector switch 300 will be rendered ineilective to forward the connection toy the operators station. Thus, if the calling condition present on the line lili results from a call initiated at the substation A and the calling subscriber hangs up, the loop circuit over which is held operated is interrupted, causing this relay to restore to open the iinpulsing circuit extending from the generator to the line relay R340. When R315!) restores, it causes the In the particular case under nerset forth above.

sequential restoration of R350 and R360 to initiate the release of the established switch train. If, on the other hand, the calling subscriber commences to dial a desired number after R319 has been caused to operate, the first pulse dialed at the calling substation caiuses R37@ to restore to reconnect the windings of the line relay Rt across the subscribers loop. Since the loop is now open, the line relay R340 restores to transmit a pulse to the vertical magnet 338. The remaining impulses dialed at the calling substation are delivered to RSM) and cause the operation of the selector switch in the man- In the event the subscribers loop circuit is opened after the generator 5&9 has started to deliver pulses to the line relay R346 but before the series of pulses is completed, the

v established switch train will either be released or the call will be routed to the wrong subs'cribers line, depending upon whether the calling subscriber hangs up or starts to dial a desired number after holding the two switches 00 and 3053 operated for a prolonged time interval.

As pointed out above, the `incoming call to the operators station 400 is indicated by the energization of the signal lamp 458 and the call may be answered through the actuation of the key switch 45B to its answer position, thereby to connect' the operators telephone to the loop extending to the ycalling substation and to open the circuitfor energizing the signal lamp M58. 'The operator atthe station 406 may now challenge the connection to determine whether the call was was occasioned by a faulty condition of the line IDI or was the result of a call initiated at the substation A. If the calling condition results from the'rst of these two causes, obviously no reply will ber received when the connection is challenged. If, on the other hand, the call to the operators station was actually initiated at the substationA, the operator may, by conversing with the calling party, determine the nature of the call, that is, whether the failure to dial a number was due to ignorance on the part of the calling party or to an emergency requiring the assistance of the operator. Assumingthat the call was originated by a party unfamiliar with the mode of operating dialing devices as conventionally employed in automatic telephone systems, the operator may either advice this party as to the operations required for obtaining the desired line, or extend the connection to the desired line in the manner conventionally employed in manual exchanges.

In many cases of emergency, such for example, as those occasioned by sudden illness, the party who initiates the call may have only sufficient time or strength to indicate that help is needed without giving any informationconcerning the point from which the call is originated.l In these cases, as in those instances where the connection to the operators station results from a faulty line condition, it is extremely desirable that the operator be able to determine the number identifying 'the calling line without assistance and with a minimum loss of time.

Operation of the apparatus to determine the number identifying the calling line and to Zoclc the calling Zine out of service I'he number or character identifying the callingI line lill may automatically be determined through the operation of the auxiliary primary line nder switch 230, the `auxiliary secondary line nder switch and the recording device 410. As indicated previously, the auxiliary primary line nder swit'ch 20) is controllable from the operators station. More specically, if the operator, upon challenging the connection ex-v tending from the line lill, deems it necessary to determine the number'identifying this line, she may initiate the operation of the switch 2% to cause tlierecording device 41E) to register the iirst two digits ofthe number identifying the calling line by momentarily actuating the key switch 4'50 to its oli-normal postion. When this operation is performed, an obvious circuit is completed for energizing the slow-to-release relay R440. This relay, upon operating, com-- pletes a holding circuit for itself, which circuit extends from ground at RAMI by way of RAMZ,

RCQM and through the winding of Rlli to yin no way affects those operated relays which depend for energization on the presence of ground on C398 or the control conductors CSi/i and Clil. This is true for the reason that the booster battery voltage is connected .in series with the exchange battery, effectively to increase the energization of those relays having windings connected to the control conductors noted. The

'application of booster battery voltage to- (13% obviously causes an increase in the positive potential on the control conductor C398 and this ncrease in potential results in the substantial energization of the line lockout relay RIZEB over a circuit extending from the positive side of the booster battery as extended to C398 by way of C3I4, CS, C98, the resistor 3l and the winding of RIZU to the negative terminal of the regular exchange battery.

When energized over the abovetraced circuit, the relay RIZ!) partially operates to close only the X contacts associated with its armatures RAIZELERAIZS and RAIZB. This partial operation of RI 2.0 serves to mark in the bank contacts of the iinder switch |99 the particular subgroup of ten lines which includes the calling line, and also to mark the particular calling line of the marked subgroup. Thus, the relay R520, by applying ground from RAI36 by way of RCiS'l and RAIZS' to the contact |58, marks the particular calling line of the marked ten-line subgroup. By applying ground from RA|35 and by way of RAIZ!) and CMS to the test contact MS of the contact set H3, the relay RIE!) marks the calling lineas being included in the first ten-line subgroup of a particular group of one hundred lines.

The partial operation of RIZ@ further results in the completion of a circuit for energizing the start relay RI Ill, this circuit extending from ground as applied to RAlSli by way of RAI28 and the winding of R! it to battery. The start relay noted is one of two such relays associated with the particular group of two hundred lines lcorresponding to the iinder switch lili?. One of these relays, namely, Rl It, is com-- monly associated with an od-d numbered group 'fill of one hundred lines associated with the iinder v finder switch |90.- Hence, through the operation.-

of the start relay Rll0, rather than the other start relay associated with the switch 00, the particular group of one hundred lines, including the calling line, is marked in the bank contacts of the auxiliary primary finder switch 20G. More specifically, when RI i0 operates, ground is applied to the rst contact 285 of the Contact set 28 over a path extending by way of RAl l2 and Cif-ll. This marking also serves to identify the particular group of one thousand lines which includes the calling line lill. At RAI I l, a path is completed for applying ground by way of CMMS to the bank contact 23h thereby to mark in the marked one thousand-line group the particular group of one hundred lines which includes the calling line. The application of ground to Cil'l further results in the energization of R220 over a circuit extending from ground on the conductor noted by way of C28?, RA23l and the winding of R220 to battery. The relay R220, upon operating, prepares, at RAZZI, a test circuit over which the upper winding of R2l0 is subsequently energized; prepares, at RA222, a holding circuit for R2I0; opens, at RA223, a point in the circuit, traced hereinafter, for energizing the release magnet 29?; prepares, at RA225, a holding circuit for the test relay R260; and completes, at RAZZA, an operating circuit :for the vertical magnet 295. The last-mentioned circuit extends from ground at RA225- by way of RA252, RC253, RAZfZ, RC243 and through the winding of the magnet 295 to battery. This magnet, upon being energized over the abovetraced circuit,l causes the wipers of the mechanism 2l0 to be translated one step vertically and attracts its armature 205 to complete an obvious circuit for energizing R250. When R250 operates, it delivers a ground pulse to the recording device 250 over a path extending from ground at RAZZI; and by way of RA252 and RA25l. The recording device responds to this ground pulse in the usual manner by recording a dash on its register tape. In a similar manner, a ground pulse is delivered to the recording device [i provided at the operators station over a path extending from ground at RA255 and by way of CEM. Thus, the two recording devices and 220 are caused to register the first verstep taken by the iinder switch 20G. When this iirst vertical step is taken, the oli-normal springs 290 are moved to the oli-normal position to prepare a circuit for energizing the release rz-iagnet 201 and a holding circuit for R230.

When the relay R250 attracts its armature RA255, it opens, at RCZSS and RA252, a point in the above-traced operating circuit for the vertical magnet 205, causing this magnet to restore its armature 205 whereby the operating circuit for the relay R250 is opened. The relay R250, upon restoring, again completes the abovetraced operating circuit for the vertical magnet 205, causing the wipers of the mechanism 270 to be translated a second step vertically and the operating circuit for R250 again to be completed at the armature 295. The relay R250 operates a second time to open the operating circuit for the vertical magnet 295 and to deliver ground pulses -to the two recording devices 250 and 070. Through the interrelated operation of the magnet 205 and R250, the wipers of the mechanism are caused to be translated vertically in a stcp-by-step manner until such time as a marked Contact in the set 204 is encountered by the test wiper Each step taken by these wipers in a vertical direction is recorded by the two devices and M0 through the operation of R250 to deliver ground pulses thereto.

In the present assumed case, the wipers of the mechanism 210 will be translated only one step a vertical direction, since immediately the firs step is completed, the test wiper 236 is brought into engagement with the marked Contact 285 to complete a circuit for energizing the lower' winding of the slow-to-operate relay R240. This circuit extends from ground at RAH2 by way of CSM, the test contact 205, the wiper 286, the lower winding of R240, RAME and through the refistor 232 and the winding ci R250 in parallel to battery. Due to the relatively high resistance of the lower winding of R240, the relay R250 does not operate when energized over the abovetraced circuit. The relay R240, however, operates, a ter an interval, to complete a holding circuit for itself, which circuit extends from ground at RAZZE by way of the x contacts associated with RAZG! and the upper winding of R250 to battery. At RAZAE, the relay R240 opens a point in the circuit for energizing the vertical magnet 255 and completes a circuit for energizing the rotary magnet 295, this latter circuit eX- tending from ground at RA224 by way of RA252,

RA2fl2, RCM-fl, RAZHS, RC2I8 and through the winding of the magnet 296 to battery.

it will be apparent that only one ground imis delivered to each of the two recording devices 250 and 470 in the particular case under consideration .since only one Vertical step on the part ci the wipers embodied in the mechanism 270 is required to iind the particular marked contact level. Hence, the calling line is identified as being included in the No. l group of one thousand lines. The next operation on the part of the auxiliary primary nder switch 200 is to select the particular group of one hundred lines which includes the calling line |05. This is achieved through the interrelated operation of the rotary magnet 200 and the relay R250 to drive the wipers of the mechanism 2l0 into engagement with the particular set of marked contacts corresponding to the group of `one hundred lines which includes the calling line. Thus immediately the rotary magnet 235 is energized, it steps the wipers of the mechanism 210 into engagement with the contacts of the rst set in the selected contact level and simultaneously completes, at its armature 206, an obvious circuit ior energizing R250. The relay R250, upon operating, delivers a ground pulse to each of the two recording devices 200 and 410 and interupts, RA252 and RC253, a point in the operating circuit, traced above, for the rotary magnet The rotary magnet again opens, at its armature 203', a circuit for energizing R250. Thus, the rotary magnet 296 and R250 are alternately en gized to drive the wipers of the mechanism il@ until such time as the wipers are stepped into engagement with the set of contacts including the marked contact 203. Since a ground pulse is delivered to each of the two recording devices 200 and G10 each time R250 operates, each step taken by the wipers is recorded by each of these two devices. It will be observed that a slight pause or time delay occurs between the end of the vertical movement of the switch wipers and the beginning of the rotary movement. This pause is caused by the slow-to-opcrate characteristic of the relay R240 and is for the purpose of spacing the dashes recorded by the two devices 200 and M0 during the vertical 75 (itl.

movement of the wipers and representing the iirst digit of the number identifying the calling line, from the dashes recorded during the rotary movement of the wipers and representing the second digit of the number identifying thev calling line. i

When, during rotary movement of the yswitch wipers, the wiper 28.1 is moved into engagement with the marked contact 281, a circuit is completed for energizing the upper winding of the test relay R218, this; circuit extending from groundv at RA1 11 by way of C140, the contact 28|, the wiper 283, the upper winding of R218, RC213, RA2|2, RA221, C288 and through the resistor 252 and the winding of R250 in parallel. `to battery. Due to the relatively high resistance of the upper Winding of R210, ythe relay R250 does not operate when energized over ythe above-traced circuit. The relay R210, however, operates and completes, at RA215, a circuit for energizing its lower winding, which. circuit eX- tends from ground at RA'ZSS by way of RA222,

RA215 and through the lower winding of R210' to battery. The relay R210 now opens, at RA2|8 and RC2l0, a point in the above-traced oper ating circuit for the rotary magnet 298, there-A by to arrest the rotary movement of the switch' wipers. lAt RA218, the relay R210 opens.y a further point in the circuit, traced hereinafter, for

energizing the release magnet 251.

At RA211, `the relay R210, upon operating, completesl a circuitr for energizing the upper winding of R158 in series' with the upper winding of Rtt, this circuit extending fromground l i., at the lower terminal of the upperv winding Aoi R238, by way of this winding, RA2| 1, the wiper 21%, the Contact 212, C118, RA132, RCHM, and` through the upper winding of R150 to battery. Due to the high resistance oi the upper winding of R150 and the relatively low resistance of vthe upper winding of R238, the relay R230 does not operate The relay R150, however, operates to open, at RAlEit, a point in they circuit, traced hereinafter, for energizing the release magnet to prepare, at RA153, a test circuit leading to the test relay R180; tol prepare, at RA152, a

holding circuit for the slow-tooperate test relay R110; and to prepare, at RAl5i, a .path forfully energizing-the lockout relayRlZii following the operation of the switch |90 tothe position corresponding to the line 181.

Following operation of R210, the operation of the primary nder switch 200 to cause 'the `two recording devices 250' and 410 tor register the first two digits of the number identifying the calling line is completed. Inthis connection, it will beapparent that, `if the contact set comprising'the marked contact28| is the fthset of the selected first contact level, ve rotary steps will be required on the part of the switch wipers before this contact set is selected. Hence, the first two digits of the number identifying the line |111 are vone and live, respectively. The final two digits of this number are recorded in response to the operation ofthe switch |90 following the operation of R210. Thus, when R210 operates, it-completes, at ,'RA216, a circuit for energizing the vertical magnet 118 and prepares, at RAZIZ, a circuit for energizing R250. The first-mentioned circuit, namely, that for energizing the magnet l|18, extendsv from ground atl '1 of the magnet |18 to battery. yThis vertical magnet, upon being energized, causes the Wipers of themechanism 155 to be translated one step vertically and attracts its armature |18 to complete the above-noted circuit for energizing R250. This circuit extends from ground at the armature 118' bywayof C118, the contact 218,

the wiper 280, RCZM, RA2l2, RA221, C288 and through'the Winding of R250 to battery. The relay R250, upon operating, Adelivers a ground pulseto each ofthe rtwo recording devices 280` and 4,18 and interrupts, at RA252 and RC253, the above-traced operating circuit for the vertical magnet 118. Y Thus, it will be seen that the magnet 113 and' 11,2513, through their interrelated operation, cause the wipers of the mechanism 155 to be translated'in a vertical direction to a "positionv opposite the marked level of contacts.

Moreover," for each step taken by these wipers a ground pulse is delivered to each of the two recording devices so that, at the conclusion of the Ivertical stepping'operation, the third digit of thev number identifying the calling line is recorded by each of vthese two devices. When the rfirst vertical step is taken by the switch wipers,

the ofi-normal springs 180 are moved to the offnormal position. At the springs |81, a circuit is prepared for energizing the magnet |16 and, at the springs 182, a holding circuit is prepared for R160.

In the present assumed case, the contact |49 standing opposite therst level of bank contacts,

is the marked contact of the test contact set |13. Hence, the wipers of the mechanism |55 will only be translated one step vertically, Yat which time the wiper 1 14 engages the test contact 149 to complete a`circuit for energizing R110, this circuit extendingfrom ground at RA| lby way of RA|20,C|48, the contact |49, the wiper 1111, C115, the lower winding of R110, RA|12, C116, the contact 218, the Wiper 280, RC2|4, RA212, RA221, C288 and through the resistor 262 and the winding of R250 in parallel to battery. Due to the relatively high resistance of the lower winding of' R110, the relay R250 does not operate whenl energized over the above-traced circuit.

` The relay yR110, however, operates, after an interval, to completegat RAI'H, a holding circuit for itself, this 'circuit extending from ground at RA|52 by way of the fc contacts associated with RAI'H andthe upper winding of R110 to battery. At RA1'12, the relay R110 opens a point in its operating circuit, as traced above. At RAMs and Rows, the yrelay R110 opens a. point than by way of RC|15 and the winding of the vertical magnet |18 to battery. The rotary magnet 111, upon being energized over the abovenoted circuit, causes the wipers of the mechanism |55 to be stepped into engagement with the iirst contact set of the selected first contact level and,

, in the above-traced 'operating circuit for the at its armature |11', completes the above-traced circuit for energizing R250. The relay R250 operates to again deliver ak ground pulse to each of the two recording devices 260 and 1110 and to open, at RA252 and RC253, a point in the circuit yfor energizing the rotary magnet |11.

With the apparatus in this condition, the rotary magnet and R250 interact to drive the Wipers 7,54v

of the mechanism |55 until they are moved into engagement with the marked contact corresponding to the line IilI, which contact, in the present case, is the contact |58. If the contact set including the contact |58 is the fourth set in the selected rst contact level, four steps will be required on the part of the wipers before this contact set is found. Hence, four ground pulses will be delivered to each of the two recording devices 26|) and 418 and the final digit of the number identifying the calling line will be recorded as four, making the complete number identifying the line IDI one-five-one-four. As indicated above, a slight pause in the operation of R259 occurs each time the dashes representing one of the digits of this number are recorded, thus insuring sufcient spacing between the dashes representing each digit to enable the digits to be separated and read. These pauses are due to the time intervals respectively required for the control apparatus to initiate the rotary movement of each of the two switches 200 and following the completion of the vertical movement and for the switch IEIEI to start operating after the operation of the switch 20D is completed.

When the wiper |59 is driven into engagement with the marked contact |58, a circuit is completed for energizing the upper winding of the test relay RIBII, this circuit extending from ground at RAI36 by way of RCIBI, RAI29, the contact |58, the wiper |59, RCI45, RAIM, RAI53 and through the upper winding of RIG to battery. The relay RIBIl, upon operating, completes, at RAIBB, a holding circuit for itself, which circuit extends from ground at the off-normal springs |82 by way of RAI 59 and the lower winding of RISO to battery. At RAISE, the relay RI 50 opens a point in the above-traced operating circuit for the rotary magnet I'II, thereby to stop the `interrelated operation of this magnet and R250 and arrest the rotary movement of the switch wipers. At RAI52, the relay RIO cornpletes a circuit for fully energizing the upper winding of R230, this circuit extending from ground at the lower terminal of the upper winding of R239 by way of this winding, RAZII, the wiper 21B, the contact 2'I2, CIIS, RAISE, RCIiS.-y and through the resistor |83 to battery. The resistance value of the resistor |83 is chosen so that the full rated current is passed through the upper winding of R235 when this winding is energized over the above-traced circuit. Hence, R236 is caused to operate to complete, at RA232, a holding circuit for itself, which circuit extends from ground at the ofi -normal springs 29| by way of RA232 and the lower winding of R236 to battery. The operation of R235 initiates the release of the switch 26 in the manner pointed out in detail hereinafter. Similarly, the operation of RIB!) initiates the release of the selected secondary iinder switch |90.

Before describing the release of the two nder switches, however, it is pointed out that RI BEI, upon operating, completes a circuit for fully energizing the lockout relay RI2Q. The circuit noted extends from ground at RAIEI by way of RAI5I, RAIIII, RCI42, the wiper I5?, the contact |56 and through the winding of R|2 to battery. The relay RI20 now fully operates to complete, at RAI2I and RAI22, a holding circuit for itself, which circuit extends from ground at RAI2I by way of CIB2, the bridge across the conductors `CI02 and Cm3, CI53, RAI22, RCI24 and through the winding of RIZIJ to battery, Since the bridge across the two conductors of the line IIlI is an integral part of this holding circuit, it will be apparent that the lockout relay is maintained energized until such time as this bridging path is interrupted. Obviously, if the bridge across the conductors C|2 and C593 is the result of a call initiated at the substation A, the holding circuit noted will be interrupted when the receiver at this station is restored to its hook. If, on the other hand, the holding bridge is caused by a faulty condition of the line or, more particularly, a short circuit between the conductors CIEl2 and CIGS, the lockout relay RIZG will only be released when the fault is cleared.

In any case, when RIZG operates, it opens, at RAI22, the loop circuit over which the line relay R428 at the operators station 49E] is held operated, causing this relay to restore to open the operating circuit for the hold relay R435. The relay R530 now restores to open, at RAMI, the hold circuit for R440 and to prevent ground from being applied to the control conductor C398 when R446 restores. At RA432 and RCZISS, booster battery potential is removed from C392. At RAI-32 and RCIIM, the negative terminal of the regular exchange battery is connected by way of the resistor 452 to C398, thereby to mark the trunk line 396 as idle in the bank contacts of the first selector switches. When R448 restores, it opens, at RAMI, the circuit for energizing the guard lamp 459, causing this lamp to be extinguished to indicate that the recording operation is complete and the operated switch train is released.

When booster battery potential is removed from the control conductor C398, the holding circuit for R335 is interrupted, causing this relay to restore to initiate the release of the selector switch 305. Similarly, the removal of booster battery potential from the control conductor noted results in the release of the finder switch IllIl and the removal of booster battery potential from the control conductor C98. Thus, the holding circuit over which the combined line and cutolf relay RISS was maintained operated, is opened and this relay restores. When RISii restores, it interrupts, at RAI33, a point in its own holding circuit and opens, at its armatures RA|35, RAI3G, and RAI39, points in the above-traced marking paths. At RAIIM, the relay RIBIJ opens a point in the operating circuit for the start relay RI Iii, causing this relay to restore to open, at RAIII, a point in the marking path' leading to the bank contacts of the switch 250 and, at RAI I2, a point in the common portion of the marking path leading to the test contact285 and the operating circuit for R220. Thus, the operated switch train extending between the line IGI and the operators station is entirely cleared out, the line IilI is locked out of service and the switches involved in the switch train are conditioned for further use.

Considering now the release of the finder switch 200, when R230 operates, it opens, at RA23I, a point in the operating circuit for R220 and, at RA233, a point in the holding circuit for REID, causing these two relays to restore. At RA224, the relay R220, upon restoring, opens a point in the common portion of the above-traced circuits by way of` which the magnets 295, 298. |13 and I'II are repeatedly energized, At RA225, the relay R22!! opens a point in the holding circuit for R240, causing this relay to restore. When the two relays R2Il and R220 fall back, a circuit is completed for energizing the release magnet 291, this circuit extending from ground at RC2 I 9 by way of RAZIS, RA223, the oir-normal springs 292 and through the winding of the magnet 297' to battery. The resulting operation of this release magnet 297 causes the wiper carriage structure of the mechanism 2l@ to be restored to normal, at which time the oif-normal springs 29B are moved to the normal position to open, at the springs to2, a point in the operating circuit for the release magnet and, at the springs 29E, a point in the holding circuit ior R233. Thus, the auxiliary primary finder switch 200 is completely released.

Considering now the release of the iinder switch itil, when the relay Rlil operates, it opens, at RAIBZ and RCIIl, a point in the previously traced circuit for energizing the upper winding of RI5, causing the last-mentioned relay to restore. falls back, it opens, at RAIEI, the above-traced operating circuit for the lockout relay RIZ; opens at RAi 52, the above-traced holding circuit for RI'iI) causing this relay to restore; opens, at

, RAI53, a point in the operating circuit'for Rltl;

and completes, at RAI54, a circuit extending by Way of the ofi-normal springs Il for energizing the release magnet H6. The resulting operation of the release magnet causes the wiper carriage structure of' the switching mechanism I55 to'be restored to normal, whereby the oit-normal springs I8@ are returned to normal to open, at the springs ISI, a point in the operating circuit for the release magnet and, at the springs iSZ, a point in the holding circuit for Rl 6E. Thus, the finder switch IQ is entirely released.

'Ihe relay RM is provided in the switch tt for the purpose of determining which of two sets of test contacts will be tested during rotary movement of the wipers embodied in the mechanism 55. More specically, the finder switch Ict has an operating position corresponding to each line oi' two, one hundred line groups and the relay Rii'l determines by its position whether the test contacts corresponding to the lines of a ten line subgroup in one of the two groups of lines will be tested during rotary movement of theswtch, or whether the test contacts corresponding to the lines of .a ten line subgroup in the other group will be tested. Since, in the case just described the line It! is included in a ten line subgroup forming a part of the odd numbered group of one hundred lines associated With the switch I9'l, it is necessary that the relay RMS be maintained deenergized during rotary movement of the switch wipers. This is insured by the operation of the switch 26H1? to select the contact set including'the marked Contact 2.3i rather than a preceding or succeeding contact set.

To clarify this point the case of a calling line included in the even numbered group of one hundred lines associated with the switch I9@ will now be briefly considered. In this last assumed case, the group start relay, corresponding to Ri It but associated with the even numbered one hundred line group which includes the calling line, marks the b-ank contact 282 ,with ground potential rather than the contact 28|. Hence, the test relay R2 lil is not caused to operate until the wipers of the switch Zware, during the rotary movement thereof, driven into engagement with the contacts of the set including the marked contact 282. In this case and when RRI@ operates,

a circuit is completed for energizing RIM, this circuit extending from ground at the lower terminal of the upper winding of R230 by wayV of v When the slow-to-release relay Ri' this winding, RAZI I, the wiper 216, the contact 2M, CHS, RAEGE, RCIG'I, the lower winding of Ritt and the winding of RIM) to battery. The resulting operation of Rld serves to prepare, at RAEIM and ROME, a test circuit which extends to REG@ from the wiper I59 rather than the wiper I59, so that, during rotary movement of the wipers embodied in the mechanism it, the contacts corresponding to the lines forming a ten line subgroup of the even numbered group of one hundred lines associated with the switch I 9c, are tested. At RAM I the relay RI 40, upon opere ating prepares a circuit for fully energizing the lockout relay associated with the calling line included in the even numbered group of one hundred lines. The relay RIS!) also operates, when energized in the above-traced circuit, to perform the functions described above.

From this point on the operation. of the apparatus and, more particularly, the finder switch ISU to cause the nal two digits of the number identiiying the calling line to be recorded, is exactly as described above. Following the operation of this finder switch to the `position corresponding to the calling line the lockout relay associated with the line is caused tol operate over a circuit extending from ground at RAII by way of RAIN, RAI-4i, ROMS, the switch wiper I5'l, the contact I 56 and the winding of the lockout reia'y, not shown, to battery. The resulting operation of the lockout relay causes the operated switch train to be released and the calling line to be locked out of service until such time as the calling condition thereon is terminated. During the release of the apparatus the relay R230 is caused to operate to initiate the release of the iinder switch 2li@ in response to its energization over a circuit different from that traced above. This new circuit extends from ground at the lower terminal of the upper winding of Rli by way of this Winding, RAZI I, the wiper 216, the Contact 2M, CI 59,7RAiIi5, RCI 6E and through the resistor I83 to battery. Obviously, the operation oi RIG!) to complete this circuit results in the deenergization of RMB. The remaining steps in the release oi the two finder switches i 9@ and Z are exactly as described above.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is contemplated tocover in the appended claims al] f such modications as fall within the true spirit extending to said operators station, whereby a connection may be established by way of said trunk line between a calling one of said lines and said operators station, line lockout means associated with the calling line, indicating means commonly associated with said plurality of lines, and means controllable from said operators station for causing said indicating means to indicate the character identifying said calling line and fory causing said locko-ut means to lock said calling line out of service.

2. In an automatic telephone system, a plurality of subscribers lines, each of said lines being identified by a particular character, a plurality of subscriber controlled automatic switches, including a group oi selector switches, for setting up connections between said lines, an operators station, each of said selector switches including a set of bank contacts terminating a trunk line extending to said operators station, whereby a connection may be established by way of said trunk line between a calling one of said lines and said operators station, line lockout means associated with the calling line, a second station remotely located with respect to said operators station, indicating means located respectively at said stations and each commonly associated with said plurality of lines, and means controliable from said operators station for causing each of said indicating means to indicate the character identifying said calling line and for causing said lockout means to lock said calling line out of service.

3. In an automatic telephone system, a plurality of subscribers lines, each of said lines being identified by a particular character, a plurality of subscriber controlled automatic switches, including a group of impulse responsive selector switches, for setting up connections between said lines, an operators station, each of said selector switches including a set of bank contacts terminating a trunk line extending to said operators station, certain of said switches other than said selector switches being effective to set up a link connection between one of said subscribers lines and one of said selector switches when a calling condition is created on said one of said lines, means only operative in the event no control impulses are transmitted to said one selector switch by way of said one line within a given time interval after said link connection is established for causing said one switch to extend said link connection by way of said trunk line to said operators station, line lockout means associated with said one line, indicating means commonly associated with said plurality of lines, and means controllable from said operators station for causing said indicating means to indicate the character identifying said one line and for causing said lockout means to lock said one line out of service until said calling condition is terminated.

4. In an automatic telephone system, a plurality of subscribers lines, each of said lines being identied by a particular character, a plurality of subscriber controlled automatic switches, including a group of impulse responsive selector switches, for setting up connections between said lines, an operators station, each of said selector switches including a set of bank contacts terminating a trunk line extending to said operators station, certain of said switches other than said selector switches being effective to set up a link connection between one of said subscribers lines and one of said selector switches when a calling condition is created on said one of said lines, an impulse generator, means included yin said one selector switch and operative during the establishing of said link connection for initiating the operation of said impulse generator, means including said impulse generator for causing said one selector switch to extend said link connection by way of said trunk line to said operatcrs station, said last-named means only being operative in the event no control impulsesare transmitted to said one selector switch by Way of said one line within a predetermined time nterval after said link connection is established, line lockout means associated with said one line, indicating means commonly associated with said plurality oi lines, and means controllable from said operators station and by way of said trunk line for causing said indicating means to indicate the character identifying said calling line and for causing said lockout means to lock said one line out of service until said calling condition is terminated.

5. In an automatic telephone system, a plurality of subscribers lines, each of said lines being identied by a particular character, a plurality of subscriber controlled automatic switches, including a group of impulse responsive selector switches, for setting up connections between said lines, an operators station, each of said selector switches including a set of bank contacts terminating a trunk line extending to said operators station, certain of said switches other than said selector switches being effective to set up a link connection between one of said subscribers lines and one of said selector switches when a calling condition is created on said one of said lines, an impulse generator, a pair of conductors interconnecting said one selector switch and said impulse generator, means included in said one selector switch and operative during the establishing of said connection for initiating the operation of said impulse generator, said generator including means for applying a control pulse to one of said conductors and means for thereafter impressing a predetermined series of impulses on the other of said conductors, a relay included in said one selector switch, said relay being arranged to be energized in response to the application of said control pulse to said one conductor and being operative to condition said one switch to respond to the impulses impressed on said other conductors, means included in said one switch and responsive to the impulses impressed on said other conductor for causing said one switch to extend said link connection by way of said trunk line to said operators station, and means responsive to impulses transmitted to saidone switch by way ol said one line for preventing the operation of said last-named means.

6. In an automatic telephone system, a plurality of subscribers lines, each of said lines being identified by a particular character, a plurality of subscriber controlled automatic switches, including a group of impulse responsive selector switches, for setting up connections between said lines, an operators station, each of said selector switches including a set of bank contacts terminating a trunk line extending to said operators station, certain of said switches other than said selector switches being effective to set up a link connection between one of said subscribers lines and one of said selector switches when a calling condition is created on said one of said lines, an impulse generator, a pair of conductors interconnecting said one selector switch and said impulse generator, means included in said one selector switch and operative during the establishing of said connection for initiating the operation of said impulse generator, said generator including means for applying a control pulse to one of said conductors and means for thereafter impressing a predetermined series of impulses on the other of said conductors, a relay included in said one selector switch, said relay being arranged to be energized in response to the application of said 

